Centrifugal pump and compressor



' 1,617,133 Feb. 8,1927. SA. Moss ET AL "CENTRIFUGAL PUMP AND COMPRESSORFiled May 23. 1925 2' Sheets-Sheet 1 Fig.1..

f O O t O O o o S Inventor: Sanford A. M 0 55,

Manuel (5. Robinson,

Their Attovneg.

r 1,617,133 Feb. 8, S. A. M ET AL CENTRIF'UGAL PUMP AND COMPRESSOR FiledMay 25, .1925 2 Sheets-Sheet 2 Inventor:

Scinford A. Moss,

Manuel GRobinsoTw,

by Their" Attorneg.

; Patented" 8 ,219,21-

v UNITED r 'ST-ATE-S PATENT ,oFFicE,

-SANIBD A... moss nn MANUEL G. ROBINSON, or LYNN, MASSACHUSETTS, As-.sIGNoRs To GENERAL ELECTRIC COMPANY, A conrona'rron on NEW YORK.

.CE'NTBIFUGAL BUM? AND oomrnnsson.

Application filed May 23, 1925. Serial No. 32,490.

The present invention. relates to. centrif- ,ugal'pumps and compressorsof the type comprising an impeller which receives the fluid to be pumpedat its central portionand I discharges it at its periphery, and wherein1913, in a centrifugal compressor for a-com-' lfl pressible fluid, suchYmeansjicomprises a passage which is firstfconvergent I and then" d1- fz'iverg fo ihei e. 0f empamt y ,h

/ 2,0,iinpe1le1: speed and .pressure' I ratio, for a @Lpassagewhichiswholly divergent formore a mal cases.

H Theobject ofcour. invent on 1s to provide ,animprovedmeans,orconstructionan'd are jrangement, for providing the passage in theiforegoing instances, forvconverting, velocity v into pressure, a, highdegree-1 of efliciency, and at jtlre sam'e timefmaintaining aconstruction which is. simple in structure and capable ofybe'ingmanufactured I at a .low fjcost, and ,foraiconjsideration of whatiwe be-[lieve to be noveland our-invention, atten .ti0n is directedjto theaccompanying, description; and the;claims appendedthereto.

{of a vccntr A I sl cing I a cent fugal compressor) "embodying ourinvention;illustrating it in its preferred 1 5- form and that 'which it.usiiall-y assumcs in X tratef modifications.

the angle between the direction of a; stream InQthe draw ng; Fig. is j asectional view gal gjmachine' f( here' '.sh'own as.

ac ual ,prac.tice,-'andj Eigs g, a and fl'illusjlates are,'broughtltogether 5259, a1id' preferably of the the outer circumferenceof the j a plates and iw lf maintainfthis constant angle, formingcalledffa ,free I vortex. '"By, tl-ie'fiangle" of the fluid inl-s'u'ch acase is meant i line at any point and the ,tangent toa circumferencepassing through that oint.

In this connection, it ispointe out that since the plates extendradially outward and the angle of the fluid remains constant, there 7results an area of discharge for the fluid which increases. continuouslyfrom the radially inner edge of the passage to its radially outer edge.In. other words, there results a divergent dischargevpassage whichfunctions to convert velocity into pressure.

The area of flow, atany circumference is given by the formula:

Area=21rrWsii1 a where 2=radius of. any circumference. w distancebetween the plates.

a=the angle of the fluid.

,From this formula it will be clear that if the angle 'a remainsconstantfthe area increases withth'e 'iadius. I Now, although thisproperty of the formation of a free. vortex has beenknown, so far as weare aware li'ttle practical use of it in centrifugalpumps andcompressorshas ever' been made this being due, we now believe, to thefact that because; of the naturally low angle of the'fluid,-thel path oftravel of the fluid in "the vortexwasso long "that the friction lossesma'de thefconversion of velocity into pressure exceedingly ineflicient.

,As -acresult, it has'been thefpractice, in con.

structing suchlcentrifugal machines, to 'pro vid'e Idischarge vanes witha divergent pas sage; for directing the flow ofth e fluid'radiallyoutward, the velocity of ,the ifi uid being at the same time convertedinto pressure;

In connectionflwithl a diffuser i-n'lthe ivyform "of two spaced annularplates, we have found that, other things being 1 equal, the, jclose'rjhcy ,7 -plates are broughfltogethenflthejh'ighei"the -Whenanjii1peller is:running,l.the fluid being handled xis;discharged from itsperi' hr]; rjyatla constant angle,"anditliskriownlt at. if; thelclischarge ;jtakesliplace' {into fa .difl'use'r formed-:- of' two-Icircular,parallehplate's', the

angle of the flfuid'lwill be, andhat thatfthe -angle of the fluid ei'results normaljfload on thes compres a .cdnstructlonrwhrein the pathoftravel of the fluid becomes short enough tomake prac tical the use ofafdilfuser'comprising'spaced annular plates ieven Ithou ghfthe radialjde th inorder to providefor the i'diifnsion necessary to effectconversion of the velocity into pressure. p

In other words, we have discovered that if the plates defining thediffusers are brought close enough together to effect an initialdirectioning of the fluid discharged from-the impeller at an angle ofthe fluid greater than 25, and then are made of a radial depth toprovide a final discharge area sufliciently great to effect the requiredconversion of velocity into pressure, that efficient operation of themachine is obtained. The correct relative positioning of the plates togive the desired angle of the fluid can be determined experimentally bypositioning the plates, and then measuring the angle of flow byinserting a freely moving vane in the stream and reading the angle whichit assumes. Or, it may be determined by calculation from the quantity offlow, speed of'the machine, and its dimensions. The required 7 radialdepth for the plates forming the diffuser can be determined also byexperiment and measurements.

In connectionwith the foregoing, it is pointedout that the angle of thefluid varies with the quantity of the fluid delivered by the impellerwhich means that, in any construction embodying our invention, if the,

quantity of the fluid being handled increases. the angle of the fluidincreases, and that if such quantity decreases the angle decreases. Incarrying out our invention we provide an arrangement such that for theloads which the machine will be required to carry ordinarily undernormal operating conditions,

the angle of the fluid will not fall below 25 for the least value ofsuch load. Preferably We construct the machine so that at normal ratedload the angle of the fluid will be of the order of 35, which means thatat normal load the highest efficiency will-be obtained. Underthesecircumstances, the angle of'the fluid will remain greater than 25,and so give eiiicient operation of the machine at loags of the order ofone-half normal rated loa I i If the tip of the impeller is suflicientlynarrow in width, the plates of the diffuser may be'par'allel throughouttheir length, but ordinarily such a condition is not met with,

so that in carrying out our invention we provide plates which approacheach other and then are parallel, or substantially parallel, the aproaching portion being such that the desire high angle of the fluid isobtained. However, the arrangement is always such 1 that the dischargearea is always increasing so as to at all times form a divergentpassage, unless conditions are such as to require a preliminaryconverging portion to effect the conversion of velocity into ressure.

Where the plates are paralie and close enough together to give thedesired angle of flow, the result may obtain that, in order to providethe necessary discharge'at the periphery of the diffuser, it assumes .acircumference too large for practical purposes, and to avoid this, theparallel portion may be followed by, a final portion wherein the platesrecede from each other. In the preferred and usual form of ourinvention, therefore, we have a diffuser structure where in the platesfirst approach each other, then are parallel, and finally recede fromeach other. This providesa passage of a length such as to give smallfriction losses and at the same time provide the desired final dischargearea without undue outer diameter of the diffuser.

Referring to the drawing, 1 indicates the casing of a centrifugalcompressor attached to which are bearings 2 in which a shaft 3 ismounted. On shaft 3 is an impeller which receives fluid at its centralportion through the inlets 5 and discharge it at its periphery to adischarge ring 6 from whence the fluid passes to a discharge scroll 7.The compressor illustrated is shown only by Way of example and is notdescribed in "detail, since its specific structure forms no part of ourpresent invention, our invention relating particularly to the dischargering 6.

Referring now particularly to the discharge ring, it is shown ascomprising walls formed in continuation of the side walls 8 for theimpeller, and as comprising a section 9 wherein the walls approach eachother, then a section 10 wherein the walls are parallel or substantiallyparallel, and finally a section 11 wherein the walls recede from eachother.

In constructing the section 9 it is desirable to make the slope of thewalls quite steep so as torapidlyincrease-the angle of the fluid, whichmay be termed the vortex angle. Ordinarily, however, the should not beso steep that the walls approach each other with a rapidit such that thedecrease in width reduces t e efi'ective discharge area faster than theincrease in diameter increases it. If such were the case, there wouldresult a converging passa e which under operating conditions usualTy metwith would effect aconversion of pres sure into velocity which wouldhave to be reconverted into pressure whereby a double energy conversionwould take place. However, if the conditions are such as to require apreliminary converging portion for conversion of velocity into pressure,then a slope so steep as to give this preliminary converging passage isnecessarily used. The sloping walls are extended radially to a pointwhere they come close enough together to give the desired vortex angleor angle of the fluid, (i. e., an angle of the fluid of at least 25.)and then they merge into the parallel or substantially parallel wallswhich form the section 10; The angle ofthe fluid is slope than 25.

.to-its radially outer edge, as already explained. This results in adivergent'passage, and the fluid in flowing through this divergentpassage has its velocity converted into pressure, as is wellunderstood.- Theparallel portion of the plates of the diffuser may bemade of a radial depth to give a final efiective area such as to eflectthe desired conversion of velocity into pressure. However, in actualpractice, this may result in" a structure of-tdo" great diameter, and toavoid this we preferably construct the final portion of the diffuserwith diverging walls so as to provide the section 11 wherein theconversion of velocity into pressure takes place at a more rapid rate.Of course, the angle of the fluid or vortex angle is less in thissection, but as such section is of small radial depth, the increase infriction loss over what it would otherwise be is not great.

. In 'Fig. 2 is illustrated a form of the invention wherein the tip ofthe impeller 12 is narrow and wherein the two plates 13 which form thediffuser are parallel throughout their radial depth, and are so closeto-. gether that the angle of the fluid is eater This forms-an eflicientdiffuser,

but as already stated, leads ordinarily to a-' constructionwherein thedifi'user is of considerable radial depth.

Fig. 3 showsa modification of the Fig. 2 arrangement wherein theradial-depth of the diffuser is shortened by providing at its periph'erya section 14 wherein the walls recede from each other. In this figure,15 is the impeller'and 16 the difl'user.

Fig. 4 illustrates an arrangement similar to Fig. 1, except that thereceding walls at.

of the diffuser are omitted the periphery and the requlred dischargearea is obtained by increasing further the diameter of the diffuser. Inthis figure. 17 is the impeller and 18 the diffuser, and as will 'benoted, the diffuser comprises, first a portion 19 wherein the wallsapproach each other, and

A then a portion 20 wherein the are parallel.

\Vhat we claim as new an desire to'seci're by Letters Patent of theUnited States,

l. A centrifugal machine having a dif tuser comprising two spaced wallsbetween which the fluid flows radially outward, said walls being soclose together that the angle.

of the fluid at normal load is greater than 25 throughout the majorportion of its:-

travel.

p 2.'A' centrifugal machine having a dif fuser comprising two spacedwalls between tween which the fluid flows outward, said walls being soshaped that the first approach each other, then extend su stantiallyparallel to each other, and then recede from each other.

3. A centrifugal. machine having a dif- 25, and then extendingsubstantially paral- .lel to maintain such angle of the fluid.

4. A centrifugal machine having adif- "fuser'comprising two spaced wallswhichprovide a discharge. passage of continuously increasing effectivearea, said walls first approaching each other to an extent such as toprovide at normal load an angle of the fluid greater than 25, and thenextending substantialy parallel to maintain such angle of the fluid. f

5. A centrifugal machine having a diffuser comprisin two spacedwallsbetween which the fluid ows radially-outward, said walls being soclose together that the an le of the fluid at normal load on the machineis of the order of.35 throughout the major portion of its travel.

--6.. A centrifugal machine having a diffuser comprising two spacedwalls between which the-fluid flows radially outward, said walls bein'so close together that the angle oftheflui at normal load is greaterthan 25 throu bout the major portion of its travel, an the peripheralortion of said walls receding. from each 0t er.

7. A centrifugal machine having a diffuser comprising two spaced wallswhich provide a discharge passage which continu ously converts velocityinto pressure, said walls first approaching each other to an extent suchas to provide an angle of the fluld at normal load greater than 25, thenextending substantially parallel to maintain such angle of the fluid,and. finally receding from each. other.

8. A centrifugal machine havin a dif fuser'comprising two spaced wallstween which the fluid flows outward, said walls first extendingsubstantially parallel to. each other and then receding from each otherat their peripheral portions. O

9. A centrifugal machine having a difprovide a dischar e passage whichcontinuously converts v e oclty into pressure, said walls approachingeach other to an extent such asto provide'at normal load anangle of thefluid of the order of 35 and then extending substantially parallel tomaintain such angle of the fluid throughout the major portion of itstravel. 1

10. A centrifugal machine having a dif? Z-fuse'r comprising two spacedwalls which I fuser comprising two spaced walls which provide adischarge passage which continuously converts velocity: into pressure,said walls first approaching each other to an extent such as to provideat normal load an angle of the fluid of the order of 35, then extendingsubstantially parallel to, each other to maintain such angle of thefluid, and finally at their eripheral portions'receding from each ot er.7 T 4 In witness whereof, we have hereunto set our hands; this 21st dayof May 1925.

SANFORD A. MOSS. MANUEL G. ROBINSON.

